<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>内部JavaScript</title>
</head>

<body>
  <div></div>
  <!-- 内部JavaScript的书写位置 -->
  <script>
    // alert弹出警示框
    alert('你好,js')
  </script>
</body>

</html>